The three-point connection devices of this invention are of the type used for connection of various kinds of work equipment at the front of a tractor. Such equipment typically operates on or near the ground at a position well in front of the front panelling of the tractor, that is, the front of the engine housing. Such front panelling is a reference location which is useful in describing this invention. Another useful reference point is the front bolster of the tractor, that is, the major lower structural member to which the front axle structure is attached.
The frontal connection devices of this invention are of the type which typically include two forwardly-extending pivotable lower links, hydraulic cylinder means acting on the lower links, and an upper link secured to an upper connecting lug. The hydraulic cylinder means, typically a pair of hydraulic cylinders, raises and lowers the lower links.
Widely varying tractor frontal connection devices have been developed over the years. In many cases, the lower links are pivotably mounted on a connection frame of the like which itself is secured to the front of the tractor. Many of such devices are add-on devices. The hydraulic cylinders are typically attached at one end to such frame and at the other end to the lower links, most typically at a position on the lower link between the pivot connection point and the distal end used for attachment of equipment. Such connection frames are attached at various points to the tractor structure, in some cases to the front bolster which also bears the front axle of the tractor.
German Offenlegungsschrift No. 3,216,589 discloses one such apparatus. In the device of such document, the lower links are mounted on laterally-spaced forwardly-extending members which are bolted at their rear ends to the tractor fastening points used for a front loader and supported at their front ends by means of brackets on the front bolster, where they are interconnected by a cross member which also serves to carry the connecting lugs for the upper link.
In such device of the prior art, the hydraulic cylinders act on rear extensions of the lower links to effect raising of said links. However, due to their approximately horizontal orientation it is not possible for the lower links to swing sufficiently up and back to properly facilitate their movement to behind the forwardmost portion of the front panelling of the tractor. As a result, even with the lower links raised, their forward protrusion poses a danger for other traffic when the front equipment is removed. As a result, placement of caution markings or other warnings are often required during vehicle movement in such condition.
In order to locate the points of pivot attachment of the lower links of a front-mounted hydraulic three-point linkage at a position far enough back on a tractor that they are in the region of the front wheels, it is known from European Pat. No. 0133637 to pivotably mount the two lower links at a position behind the forwardmost point of the front panelling of a tractor, and also to locate the hydraulic cylinder means at such position. However, such arrangements fail to consider other important requirements for frontal connection apparatus, including the need to accommodate a power take-off shaft, ballast weights, and a draft jaw.
Another disadvantage of such known arrangement is that, due to the overall configuration of the device and orientation of the hydraulic cylinder in such arrangement, the lower links cannot be retracted fully behind the forwardmost point of the front panelling when not in use. It is necessary that they be removed entirely if they are not required, and removal is a fairly difficult operation.
Referring to other prior art, it is known from German Offenlegungsschrift No. 2,758,978 to fasten a unitary casting on the front side of the front bolster, with such casting being used as the bearing element for front-mounted implement hitch means, including the hydraulic lifting cylinder. It is noteworthy that such casting device has a central recess access to a front-mounted power take-off shaft and, below such access means includes an integral draft jaw.
In such arrangements, it is a disadvantage that the upper and lower links project so far forward that they impair connection of an implement to the power take-off shaft. Such extreme forward projection also requires removal of the links to allow connection of an implement to the draft jaw. Furthermore, with or without an implement connected to the upper and lower links, the lower links cannot be swung behind the front surface of the front panelling. The positioning of the hydraulic cylinder in front of the front panelling further blocks such retraction of the lower links.
German Offenlegungsschrift No. 3,209,849 discloses a front-mounted power lift mechanism for tractors which has lower links pivotably secured to laterally-spaced bearing plates. The lower links are swung by vertically orientated hydraulic cylinders and are interconnected by a cross member which is in front of the front panelling of the tractor. The orientation of the cylinders and the presence of the cross member prevent retraction of the lower links behind the front surface of said panelling. The laterally-spaced bearing plates are interconnected in their upper front regions by a cross-member which carries connecting lugs for the upper link. However, there is no provision for the carrying of ballast weights.
German Offenlegungsschrift No. 3,306,415, noting the problems associated with the forward projection of frontal connection devices and the difficulty of removing links, deals with the problem by providing a bumper which is secured to the front ends of the lower links, rounded off at the sides and the front in the direction of collision, and covers the front ends of the lower links in all positions. However, a disadvantage of this arrangement is that the bumper has to be removed in order to couple implements to the power lift mechanism.
German Offenlegungsschrift No. 2,718,959 discloses a tubular member into which journals for locating the rear ends of the lower links can be inserted. However, the journals are not connected to the lower links but instead pass through the links and through plates fixed thereto. This patent is noted here only for its minor visual similarity to a single feature of the invention herein.
There are a variety of additional shortcomings and problems and in devices of the prior art. Many devices are most difficult to connect and disconnect. Others are complex and frequently in the way. Still others impede the use or operation of other devices on the tractor. For others, operation can be problematic.
There is a well-recognized need for an improved tractor frontal connection apparatus.